U.S. Pat. No. 4,080,486 describes a protective coating system for nickel base and cobalt base superalloy substrates, such as turbine blades and vanes, exposed to high temperature in a gas turbine engine. The patented coating system comprises an MCrAlY type overlay coating, where M is an element selected from the group consisting of iron, nickel and cobalt, that is aluminized by pack cementation to increase the corrosion and oxidation resistance of the coated substrate.
An object of the present invention is to provide a chemical vapor deposition (CVD) aluminide diffusion overcoated MCrAlY coating system having substantially improved high temperature oxidation resistance.
Another object of the present invention is to provide a CVD coating method for making an aluminide diffusion overcoated MCrAlY coating system having substantially improved high temperature oxidation resistance.
A further object of the present invention is to provide a CVD aluminide diffusion overcoated MCrAlY coating system on an exterior of the substrate and a CVD aluminide diffusion coating on an interior of the substrate and method for making same.